Former Premier League referee has insisted that Liverpool should have been awarded a penalty for Shane Long's challenge on Roberto Firmino against Southampton.
The Reds went on to claim a comfortable 4-0 win at Anfield which moved them 22 points clear at the top of the Premier League table.
Goals from Alex Oxlade-Chamberlain, Jordan Henderson and a brace from Mohamed Salah made the difference in the second half.
However, Liverpool felt they should have had a penalty in the first half after Long appeared to drag down Firmino, with the striker set to head home a cross from close range.
Kevin Friend waved away the appeals and VAR concurred with the on-field official, much to the surprise of everyone inside Anfield.
That came as a shock to Gallagher too, who believes the Reds were denied an obvious penalty kick.
“I thought it was a penalty. He knows exactly what he is doing, he brings him down," he told Sky Sports Ref Watch.
"The VAR felt that there was minimal contact on his shoulder to bring him down.”
Equally, Southampton felt aggrieved not to have been awarded a penalty themselves in the build-up to Liverpool's opening goal.
Danny Ings felt that he was tripped in the penalty area by Fabinho, only for Oxlade-Chamberlain to race up the other end to fire Liverpool ahead.
Friend once again waved away Ings' claim, with VAR agreeing with the initial decision.
Similarly, Gallagher agreed that there was not quite enough contact for Ings to be awarded a spot-kick.
Gallagher said: “I think he has fast feet, he goes around and I think Fabinho touches the ball, they go up the other end and scores.
"I saw that and thought ‘he got the ball, play on’ which the referee did. No (not a penalty).”
